Hypothalamic neuropeptide Y (NPY) gene expression is not affected by central serotonin in the rainbow trout (Oncorhynchus mykiss).

Mammalian studies have shown a link between serotonin (5-HT) and neuropeptide Y (NPY) in the acute regulation of feeding and energy homeostasis. Taking into account that the actions of 5-HT and NPY on food intake in fish are similar to those observed in mammals, the objective of this study was to characterize a possible short-term interaction between hypothalamic 5-HT and NPY, by examining whether 5-HT regulates NPY gene expression, to help clarify the mechanism underlying the observed anorexigenic action of central 5-HT in the rainbow trout. We used qRT-PCR to determine the levels of NPY mRNA in the hypothalamus-preoptic area (HPA) of rainbow trout after intraperitoneal (i.p.) injection of a single dose of dexfenfluramine (dFF, 3mgkg(-1); 24h-fasted and fed fish) or intracerebroventricular (i.c.v.) administration of 5-HT (100µgkg(-1); 24h-fasted fish). Significant suppression of food intake was observed after administration of 5-HT and dFF. No significant changes in NPY gene expression were obtained 150min after administration of 5-HT or dFF. However, administration of the 5HT1B receptor agonist anpirtoline did not have any significant effect on food intake in rainbow trout. The results suggest that in fish, unlike in mammals, neither the NPY neurons of the HPA nor the 5-HT1B receptor subtype participate in the neural circuitry involved in the inhibition of food intake induced by central serotoninergic activation.

Cardiovascular safety of low-dose fenfluramine in Dravet syndrome: a review of its benefit-risk profile in a new patient population.

OBJECTIVE: Dravet syndrome (DS) is a rare, treatment-resistant epilepsy syndrome for which current treatment regimens are often ineffective. Fenfluramine is currently in development for treatment of DS, based on reports in the 1980s and 1990s of its anti-epileptic activity in pediatric patients with intractable epilepsy. However, fenfluramine was withdrawn from global markets in 1997 following reports of its association with pulmonary hypertension and heart valve disease in adult patients treated for obesity. This review was conducted to assess cardiac safety of fenfluramine when used at lower doses for treatment of DS. METHODS: Pubmed was searched for clinical studies of fenfluramine in obese adults who reported incidence of heart valve disease. These data were reviewed against published results from Belgian patients with DS who have been treated with low-dose fenfluramine for up to 28 years. RESULTS: Nine controlled studies of fenfluramine and related compounds (dexfenfluramine and/or phentermine) which assessed incidence and severity of cardiac valve disease in 3,268 treated patients and 2,017 control subjects have been reported. Mild or greater aortic valve regurgitation was found in 9.6% of treated patients compared with 3.9% of control subjects, and moderate or greater mitral valve regurgitation was found in 3.1% of treated patients and 2.5% of control subjects. Nineteen DS patients have been treated for up to 28 years with 10-20 mg/day fenfluramine, with no clinical signs or symptoms of cardiac valve disease or pulmonary hypertension. Slight and clinically unimportant changes in valve structure have been seen on echocardiography in five patients at some time during the observation period. CONCLUSIONS: A different benefit-risk relationship appears to be emerging when fenfluramine is used at low doses for extended periods in young patients with DS. Continued cardiac assessments during ongoing Phase 3 clinical trials will provide additional safety information for this potential new and effective treatment.

Appetite suppressants and valvular heart disease in a population-based sample: the HyperGEN study.

PURPOSE: Previous studies of the association between the use of appetite suppressants and valvular heart disease have not accounted for the effects of valvular structure and aortic root diameter, which are associated with obesity. We assessed whether the use of the appetite suppressants fenfluramine/dexfenfluramine, either alone or with phentermine, was associated with aortic regurgitation while adjusting for these variables. SUBJECTS AND METHODS: The sample included 2524 adult participants in the population-based Hypertension Genetic Epidemiology Network study. Information regarding current drug use was assessed during a clinical examination. Medication use was continued at the time of echocardiographic study. Expert readers blinded to current therapy read echocardiograms centrally at Cornell Medical Center. Analyses of the associations between use of fenfluramine/dexfenfluramine (alone or with phentermine) and aortic regurgitation adjusted for potential confounders, including aortic root dilatation and valve fibrocalcification. RESULTS: Nineteen participants, all of whom had hypertension, were being treated with fenfluramine or dexfenfluramine (5 on these agents alone, 14 also with phentermine). Aortic regurgitation was present in 32% (n = 6) of those taking fenfluramine or dexfenfluramine versus 6% (162/2505) of remaining subjects (P = 0.001). In multivariate-adjusted analyses, treatment with fenfluramine or dexfenfluramine was associated with aortic regurgitation (odds ratio [OR] = 4.9; 95% confidence interval [CI]: 1.7 to 14) and aortic fibrocalcification (OR = 5.2; 95% CI: 1.9 to 15). CONCLUSION: In a population-based sample, use of fenfluramine or dexfenfluramine, alone or in combination with phentermine, was associated with aortic regurgitation independent of aortic dilatation or fibrocalcification.

Acute anorectic effect of single and combined drugs in mice using a non-deprivation protocol.

RATIONALE: Studies of the effect of anorectic drugs such as fenfluramine in mice have indicated the desirability of using experimental protocols that do not involve deprivation. OBJECTIVE: We have developed a non-deprivation or "dessert" protocol for use in mice that are maintained in standard housing conditions, and examine the effects of a serotonergic agent dexfenfluramine (DFEN), a dopaminergic agent phentermine (PHEN), and a selective norepinephrine uptake inhibitor thionisoxetine (TNIX) alone and in combination. METHODS: Female C57BL/6J mice were adapted to 30 min daily presentation of a gelatinized form of sweetened milk using a holder that hooks over the side of the cage during tests; food spillage and contamination are minimal. Dose-inhibition curves were determined for DFEN, PHEN, and TNIX alone and for fixed ratio combinations of DFEN with either PHEN or TNIX. RESULTS: Each drug produced a near linear dose-inhibition curve with the 50% inhibitory doses (DI50) of 5.6, 3.2 and 12.2 mg/kg, respectively. By isobolographic analysis, the effects of the drug combinations were strictly additive. CONCLUSION: The procedure described is highly suitable for testing anorectic drugs in mice and is adaptable to a variety of housing conditions and diets. The DFEN+ PHEN combination was additive, which contrasts with its reported supra-additive effect in rats.

Activation of hypothalamic insulin by serotonin is the primary event of the insulin-serotonin interaction involved in the control of feeding.

In previous experiments, we reported a close parallelism in the responses of both serotonin (5-HT) and insulin in the hypothalamic PVN-VMH region of freely-moving rats during feeding. Thus, hypothalamic 5-HT and insulin may participate, independently or in interaction, in the control of carbohydrate and fat ingestion. The precedence of the activation of one or the other substance remained to be investigated. In adult male Wistar rats, (a) dexfenfluramine was administered to the PVN-VMH region by reverse microdialysis (80 microM for 10 min) while local insulin was assessed; (b) insulin was locally infused (400 mU for 10 min) through the tip of the dialysis probe while 5-HT was measured. Dexfenfluramine immediately increased 5-HT release, and also extracellular insulin levels (+102%). This activation of insulin by serotonin is actually a central effect since neither insulinemia nor glycemia were affected. Conversely, insulin enhanced 5-HT release (+81%), but only 45 min after the beginning of its infusion. Noradrenaline, dopamine and metabolites were slightly or not at all modified by insulin. These data demonstrate that an interaction does exist between insulin and 5-HT in the VMH-PVN area. Because of the delay of 5-HT response to insulin, an activation of the serotonergic system would be the causal event acting immediately on insulin, and not the contrary. Whatever the exact mechanism of this interaction, it seems to be a link in a larger cascade of events involving numerous neurotransmitters and peptides leading to the regulation of feeding.

Effects of prenatal co-administration of phentermine and dexfenfluramine in rats.

Pregnant rats were infused with phentermine plus dexfenfluramine from days 3 through 17 of gestation. Control rats were either pair-fed or were fed ad libitum. There were no effects of prenatal drug treatment on number of offspring, their birth weights, or on their motor coordination assessed at 11 days of age. Mothers and pups were sacrificed 21 days postpartum. Drug-treated mothers, but not their pups, showed a reduced density of serotonergic axons in the hippocampus compared with controls. 25% of the pups from the prenatal drug group showed mitral valve thickening.

Effect of repeated administration of dexfenfluramine on feeding and brain Fos in mice.

The present study examines whether repeated administration of dexfenfluramine (DFEN) to mice is associated with progressive attenuation of its anorectic action and induction of Fos-immunoreactivity (Fos-ir) in some brain regions, both known effects in rats. ICR:Cd-1 mice were adapted to receiving for 30 min daily a sweetened milk gelatin dessert in addition to ad libitum access to chow. Mice were then injected with either DFEN (5-10 mg/kg) or saline vehicle every other day. These doses of DFEN acutely suppressed intake by approximately 50% and this action was sustained for at least eight injections. The anorectic effect of DFEN was no different between drug-naïve and DFEN-pretreated mice under conditions that produce complete tolerance in rats. In addition, unlike in rats, the acute anorectic effect of m-chlorophenylpiperazine (mCPP) was unaffected by prior DFEN treatment. Mice were perfused after the intake test on the final experimental day and their brain processed for Fos-ir. DFEN induced Fos-ir in brain regions analogous to those reported in rats and, also, as in rats, DFEN pretreatments reduced substantially the Fos-ir induced by acute DFEN in regions including central nucleus of amygdala, bed nucleus of stria terminalis, and the paraventricular hypothalamus (magno- and parvocellular divisions; PVN). Thus, while DFEN pretreatments reduce the effects of DFEN in many brain regions in both rats and mice, mice are unlike rats insofar as there is no tolerance to the anorectic action, at least in the nondeprivation protocol used here.

Effects of amphetamine, dexfenfluramine, and diazepam on responding during extinction in nonhuman primates.

The effects of pharmacological manipulations on responding under extinction conditions were determined in baboons using a schedule of reinforcement that modeled food acquisition and food consumption. Responding during the initial acquisition component was reinforced by stimuli paired with food, while responding during the latter consumption component was reinforced with food. Certain sessions began with a 7-h extinction phase, where responding in both components produced only the paired stimuli. Dexfenfluramine (DFEN) decreased responding during extinction. Diazepam (DZP) increased responding during extinction. Low doses of amphetamine (AMPH) increased responding during extinction. Thus, DZP and AMPH increased and DFEN decreased the conditioned reinforcing effects of stimuli paired with food.

Effects of anorectic drugs on food intake under progressive-ratio and free-access conditions in rats.

The effects of two anorectic drugs, dexfenfluramine and phentermine, on food intake under different food-access conditions were examined. Experiment 1 compared the effects of these drugs on food intake under a progressive-ratio (PR) schedule and free-access conditions. Dexfenfluramine decreased food intake under both conditions, but the doses required to decrease intake under free-access conditions were higher than those required to reduce intake under the PR condition. Intermediate doses of phentermine sometimes increased breaking points, and higher doses decreased them. Phentermine decreased food intake at the same doses under both access conditions. Thus the potency of dexfenfluramine, but not phentermine, to decrease food-maintained behavior depended upon the food-access condition. Experiment 2 used a novel mixed progressive-ratio schedule of food delivery to study the duration of drug effects. Sessions consisted of five components separated by 3-hr timeouts. The ratio requirement reset at the beginning of each component and a new breaking point was obtained. Both dexfenfluramine and phentermine dose-dependently decreased breaking points early in the session. In some rats, compensatory increases in breaking point were observed. That is, breaking points later in the session increased over control levels, resulting in no change in the total number of food pellets earned for the session compared to control. The present findings suggest that the effects of some anorectic drugs depend upon the access conditions for food; increasing the effort to obtain food may enhance their ability to decrease food-maintained behavior.

[Anorectics and pulmonary hypertension]. / Anorektika a plicní hypertenze.

Anorectics (appetite-suppressant drugs) are frequently requested by patients. Their usage, however, can have serious, life-threatening side effects, such as pulmonary hypertension and valve defects. The association of anorexigen use with pulmonary hypertension was first detected at the end of the sixties. Back than, the incidence of pulmonary hypertension, diagnosed as primary, increased soon after an anorexigen, aminorex was introduced. After aminorex was recalled several years latter, the incidence of the disease returned to the usual low levels. A recent epidemiological study proved that a newer anorexigen, fenfluramine (or its stereoisomer, dexfenfluramine) considerably increases the risk of pulmonary hypertension. Currently, it is unclear how the anorectics contribute to the development of pulmonary hypertension. One possibility may be the increase in plasma serotonin concentration. Serotonin is a pulmonary vasoconstrictor in many species. However, even if this mechanism plays any role in humans, it cannot completely explain the influence of anorectics on the pulmonary circulation. The anorectics cause membrane depolarization of the pulmonary vascular smooth muscle cells by inhibiting potassium channel activity. The depolarization activates voltage-operated calcium channels, thus increasing intracellular calcium ion concentration, which is the well-known stimulus for vasoconstriction. The increase in vascular tension can be especially significant when there is a deficiency in mechanisms acting against vasoconstriction, such as endothelial production of nitric oxide (NO). Such pre-existing defects may be the reason why only a fraction of patients using anorectics actually develop pulmonary hypertension.

[Appetite depressants and pulmonary hypertension]. / Appetitzügler und pulmonale Hypertonie.

In 1996 the total number of prescriptions of the appetite depressant drugs fenfluramine and phentermine exceeded 18 million in the United States. Clinical observation and experimental evidence back in the early 1980's showed that these drugs can cause a pulmonary hypertension. We report the case of a 30-year old woman with a history of seven month medication with dexfenfluramine. She developed severe pulmonary hypertension and right heart failure during late pregnancy. She died of septicemia with multiorgan failure 4 days after cesarean section. Pulmonary hypertension has been reported in association with treatment with fenfluramine and dexfenfluramine. These drugs may cause the increased precapillary resistant pressure through the vasoconstrictor action of serotonin. The typical histological finding is a plexogene pulmonary arteriopathy and valvular heart disease. After these observations the drugs were withdrawn.

Characterizing the effects of 5-HT(2C) receptor ligands on motor activity and feeding behaviour in 5-HT(2C) receptor knockout mice.

5-HT(2C) receptor agonists have considerable therapeutic potential, however there is little in vivo data to compare the potency and selectivity of 5-HT(2C) receptor agonists. Since 5-HT(2C) receptor agonists reduce locomotor activity and food intake, changes in these drug-induced behaviours in 5-HT(2C) receptor knockout mice could provide a means to examine receptor selectivity in-vivo. Initially this study compared older 5-HT(2C) agonists mCPP and MK212, to newer, apparently more selective compounds: Ro 60-0175, WAY161503, CP809,101 and lorcaserin (APD356) on motor activity in wild-type, and 5-HT(2C) receptor knockout mice. Two 5-HT(2C) receptor antagonists SB242084 and SDZ SER 082 were also examined. mCPP did not significantly alter activity in wild-type mice, but enhanced activity in knockout animals. MK212 (3 and 10 mg/kg) and Ro 60-0175 (1 and 3 mg/kg) reduced activity in wild-type but not knockout animals. At 10 mg/kg, Ro 60-0175 reduced activity in knockout animals, suggesting loss of 5-HT(2C) receptor selectivity. CP809,101 and lorcaserin reduced activity in wild-type but not knockout mice. In subsequent feeding studies, Ro 60-0175 and lorcaserin reduced food intake in wild-type animals only. Selectivity of effect for mCPP was marginal. The antagonist SB242084 increased activity in wild-type animals but not in knockout mice; SB242084 did not alter feeding in either genotype. SDZ SER 082 reduced activity in both genotypes implying poor selectivity for 5-HT(2C) receptors. The data demonstrate that studying food intake, and particularly motor behaviour, in the 5-HT(2C) receptor knockout mouse is a useful and relatively simple approach for screening 5-HT(2C) receptor ligands in vivo.

Efficacy of dexfenfluramine in the treatment of alcohol dependence.

BACKGROUND: A substantial body of evidence supports a role for serotonin in modulating alcohol intake, which suggests that this neurotransmitter represents a promising target for pharmacotherapy development for alcohol use disorders. Dexfenfluramine. a serotonin releaser and reuptake inhibitor, decreases alcohol self-administration by rats. Its greater potency and several mechanisms of action suggest it should be more effective in treating alcohol dependence than drugs that only inhibit serotonin reuptake. METHODS: We conducted an 11 week, randomized, double-blind trial that compared oral placebo and dexfenfluramine 7.5, 15, 22.5, and 30 mg bid in 136 alcohol-dependent patients. A brief behavioral intervention was offered concurrently. RESULTS: The majority of subjects were male (72%), and the age of the group was 44 +/- 1 years (mean +/- SD). Both placebo- and drug-treated groups significantly reduced alcohol consumption compared with baseline (a 55% decrease in mean drinks per day; p < 0.01), but there were no significant differences between drug and placebo groups or dose effects for most outcome measures. CONCLUSIONS: Our results with dexfenfluramine are further evidence that serotonergic medications on their own do not significantly reduce alcohol consumption in alcohol-dependent individuals. Combination pharmacotherapy with agents that act on different receptors or neurotransmitter systems (e.g., naltrexone plus dexfenfluramine) may be one way to enhance serotonergic effects on drinking behavior and should be considered in future medication development clinical trials.

Decreased androgen levels in massively obese men may be associated with impaired function of the gonadostat.

OBJECTIVE: In obese men, sex hormone-binding globulin (SHBG) as well as total testosterone (TT) levels are decreased. Data concerning serum free testosterone (FT) levels in obese men are discordant. FT levels are decreased in only some morbidly obese men, consistent with an impairment of the feedback regulatory mechanism. In this study we aimed to verify serum levels of TT and FT in two groups of obese men (BMI < 35.0 kg/m2 and BMI > 35.1 kg/m2) before and after weight loss. DESIGN: Two groups of obese men (group 1: BMI < or = 35 kg/m2; and group 2: BMI > or =35.1 kg/m2) were studied before and after 6 months of a low energy diet (1200 kcal/day). Every patient received a therapeutic prescription of dexfenfluramine (15 mg b.i.d.) that was maintained for 6 months. SUBJECTS: Thirty-seven obese men and 20 normal weight men. MEASUREMENTS: Serum sex hormones (TT and FT), serum luteinizing hormone (LH) and insulin were analyzed by RIA assays. Plasma insulin levels, serum TT, FT and LH concentrations were obtained before and after weight loss. RESULTS: Moderately obese men (BMI = 32.3+/- 1.9 kg/m2) presented significantly decreased TT levels (390+/-120ng/dl) as well as FT (mean+/-s.d.:16.0+/-4.8pg/ml) as compared with normal controls. FT serum levels had a significant and negative correlation with body mass index (BMI), whereas for TT concentrations this correlation was not significant. Serum LH concentrations (4.5+/-2.9mlU/ml) were normal. Insulin levels were elevated in all patients (46.3+/-30.1 microU/ml). After weight loss there was a significant (P< 0.01) increase in TT, FT and LH levels, whereas insulin concentrations significantly decreased. In massively obese men (BMI = 43.0 6.7 kg/m2), TT (320+/-110ng/dl), FT (11.0+/-2.1 pg/ml) and LH (3.1+/-1.3mlU/ml) were decreased and significantly lower as compared with the previous group and normal controls. As expected, after weight loss TT, FT and LH levels increased significantly while insulin concentrations decreased. CONCLUSIONS: We concluded that FT levels are dependent on the degree of obesity, massively obese men (BMI > or =35.1 kg/m2) being considered as candidates for consistently low FT levels. A functional decrease of LH pulse amplitude and serum LH levels as well as a possible negative action of excess of circulating leptin on the steroidogenesis may be related to the decreased androgens levels in massively obese men.

A comparison of sibutramine and dexfenfluramine in the treatment of obesity.

OBJECTIVE: Because long-term weight reduction is often unsuccessful with dietary restriction alone, pharmacological agents have been used to promote weight loss. We have compared the novel (multiple monoamine neurotransmitter reuptake inhibitor) antiobesity drug sibutramine (10 mg once daily) with the extensively studied serotonin-releasing antiobesity agent dexfenfluramine (15 mg twice daily). RESEARCH METHODS AND PROCEDURES: 226 healthy outpatients (aged 18 to 65 years; body mass index > or =27 kg/m2) were included in a 12-week, randomized, double-blind, parallel group study. The main outcome measures were changes in weight, body mass index, waist and hip circumference and ratio, and safety profiles. RESULTS: Mean (+/-SEM) absolute weight loss was 4.5 +/- 0.4 kg in the sibutramine group (n = 112) and 3.2 +/- 0.3 kg in the dexfenfluramine group (n = 112) (endpoint analysis); 4.7 +/- 0.4 kg in the sibutramine group (n = 101); and 3.6 +/- 0.3 kg in the dexfenfluramine group (n = 94) (completers analysis). Comparing the two treatments under the conventional null hypothesis of equality as a secondary analysis, weight loss at endpoint in patients receiving sibutramine was significantly greater than that achieved with dexfenfluramine (p<0.05). Both drugs had similar adverse events profiles: 174 patients (77%) experienced adverse events; 17 patients withdrew due to adverse events (sibutramine, n = 6; dexfenfluramine, n = 11). Pulse rate increased significantly in sibutramine-treated patients (3.6 bpm), but decreased in dexfenfluramine-treated patients (-0.9 bpm). DISCUSSION: Sibutramine (10 mg once daily) is at least as effective as dexfenfluramine (15 mg twice daily) in achieving weight loss in patients with obesity.

Effects of dexfenfluramine on aristolochic acid nephrotoxicity in a rat model for Chinese-herb nephropathy.

Chinese-herb nephropathy (CHN) is a progressive renal interstitial fibrosis initially reported after concomitant intake of an anorexigen, (dex)fenfluramine, and a Chinese herb ( Aristolochia fangchi) containing nephrotoxic and carcinogenic aristolochic acid (AA). We thus tested the possible enhancing effect of the active enantiomer dexfenfluramine (DXF) on AA nephrotoxicity in a rat model for CHN. Groups of 12 salt-depleted male Wistar rats received daily subcutaneous injections of 7 mg/kg body weight DXF (DXF group), 7 mg/kg body weight AA (AA group), a combination of the same doses of AA and DXF (AA+DXF group), or vehicle (control group) for up to 35 days. Six animals per group were killed on day 10 and the remaining six on day 35. Renal function was evaluated by determining serum creatinine and urinary leucine aminopeptidase activity. Histological evaluation of kidney samples was performed and tubulointerstitial injuries were semiquantified. The DXF group did not differ from controls for any parameter. Similarly elevated serum creatinine levels, decreased leucine aminopeptidase enzymuria, and renal lesions were observed in the AA and the AA+DXF groups after both 10 and 35 days. The formation of specific AA-DNA adducts in liver and renal tissue samples was assessed by the (32)P-postlabelling method. Specific AA-DNA adduct levels were significantly increased in kidney tissues from AA+DXF rats compared with AA rats. These functional and histological data suggest that DXF does not enhance AA nephrotoxicity in a rat model for CHN. Further investigations are needed to clarify the mechanism by which DXF may enhance AA-DNA adduct formation.